In a food processor or blender, add beans, 2 eggs and vanilla. Pulse several times until beans are broken up. Add 1/2 cup of cocoa powder and blend until smooth and no lumps remain.

In a large bowl, cream the butter, sugar and salt. Add remaining egg and mix well. Add bean mixture. Stir until well incorporated.

Grease an 8×8-inch square baking dish. Pour in batter, tapping lightly to remove any bubbles. Bake for 35 to 45 minutes, or until toothpick inserted into centre of brownie comes out clean.

Allow brownie to cool to room temperature. In a large bowl add brownie and crumble. Chill for 1 hour.

Line a cookie sheet with parchment paper. Once brownie crumble is firm, remove from fridge and form into 1-inch balls. Place on cookie sheet and chill for 15 minutes.

In a large bowl, add remaining 1/4 cup of cocoa powder. One at a time, roll chilled truffles in cocoa powder, tapping off any excess. Serve on a platter or store in an airtight container, separating the layers with parchment.